Means for controlling and regulating electric motors.



PATENTED SEPT. 6, 1904.

G. RENNERFELT. MEANS FOR CONTROLLING AND RBGULATING ELECTRIC MOTORS.

APPLICATION FILED NOV. 9. 1903.

no MODEL.

3 SHEETS-SHEET 1- v ATTORNEY WITNESSES.-

No. 769,406. PAT'ENTED SEPT. 6, 1904. G. RENNERPELT. MEANS FORGONIROLLINGAAND REGULATING ELECTRIC MOTORS.

APPLICATION FILED NOV. 9.1903- .10 MODEL. 3 SHEETS-SHEET 2.

7 4c E y-5 52 u HE 38 0% W/T/VESSEQ: 4W W :6. 62M;

MZQ 16W PATENTED SEPT. 6, 1904.

G. RENNERPELT. MEANS FOR CONTROLLING AND REGULATING ELECTRIC MOTORS.

APPLIGATION FILED NOV. 9. 1903.

3 SHEETS-SHEET 3 K0 MODEL.

' Patented September 6, 1904.

PATENT OFFICE.

GUSTAF RENN'ERFELT, OF NEW YORK, N. Y.

MEANS FOR CONTROLLING AND REGULATING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 769,406, datedSeptember 6, 1904. I Application filed November 9, 1903. Serial No.180,447. No model.)

To all whom it may concern:

Be it known that I, (iUS'fAF Rusnsnrmxr, a

subject of the King of Sweden and Norway,

for preventing abnormal speeding of an clec-' tric motor upon startingthe same; third, to provide novel means for automatically rupturing thecurrent flow through an electric motor in the event of an overheating ofthe same; fourth. to devise apparatus in which all the aforesaid threeobjects will result automatically and in which the manual operationshall be limited to the closing of a single electrical contact, and,fifth, to so arrange said apparatus that a minimum amount of energy willbe wasted in its operation and also so that it shall be simple and cheapin construction.

My invention will be fully understood by referring to the accompanyingdrawings, in

which- Figure 1 is a side elevational view of a part of the controllingapparatus supported upon an insulating base or board, the lower portionof said apparatus being shown in sectional view. Fig. 2 is a detailsectional view taken through Fig. 1 on the line X X and as seen lookingthereat from the top toward the bottom of the drawings. Fig. 3 is a partside elevational part-sectional view taken through Fig. 2 on the brokenline Y Y and as seen looking thereat from left toright. Fig. 4 is adetail sectional view of that portion of the apparatus which prevents atoo-sudden starting of the motor; and-Fig. 5 is a sectional view takenthrough the body of Fig. 4 and as seen looking thereat from right toleft. Fig. 6 is a diagrammatic view illustrating the currentmains,branch feeders, and the motor to be controlled, together with my novelapparatus, circuits. and circuit connections as applied thereto. Fig. -7is a view of the switching parts similar to the like parts shown in Fig.

-1 with a reversing-switch instead of a single switch. Fig. 8 is ahorizontal sectional view of Fig. 7, taken on the line Z Z,with theswitching parts shown in plan', the manner of attaching the same to theswitchboard being also shown. Fig. 9 is a diagrammatic view similar toFig. 6, but illustrating the circuit connections and application or useof the reversing-switch (shown in Figs; 7 and 8) in relation thereto.

In the use of electric motors as heretofore regulated and controlled anattendant may often carelessly switch the current through the motor insuch quantity as to seriously damage the same, and particularly is thistrue when the motor is carrying or moving a relatively heavy load. Italso often occurs that the motor may be started with greateracceleration than desirable, and particularly is this true when themotor is moving a relatively light load. Myinvention is designed toovercome these objections, and to this end 1 use a pilot-motor forintermittently moving the regulator,'its movement being stopped when thestarting-current exceeds a predetermined limit and also when theacceleration rate exceeds a predetermined limit, and means are providedwhereby both of said limits can be easily adjusted, so that the sameapparatus may be used for diflerent motor installations with varyingrequirements.

My invention also comprises novel apparatus whereby the motor itselfwhen started too suddenly will act so as to automatically preventfurther moving of the regulator, and this 1 effect through the agency ofan acceleration-controller not generically difi'erent from thatdisclosed in a prior patent grantedto me on the 16th day of May, 1899,by the United States Patent ()flice and bearing No. 625,060, socombining the same with the pilotmotor that its circuit is interrupted.

Referring now to the drawings in detaii for a full and clearunderstanding of my invention, in all of which like numerals and lettersof reference represent like parts wherever used, and first to Fig. 1, 8represents the controller-switchboard, made, preferably, "of marble orother insulating material, and t a pilot-motor for regulating themovement of the controller, the armature and field circuits 52, ournaledin standards. as shown, and

. of said motor being located in a branch circuitf, controlled by anoperating-switch Su', as will be more particularly described inconnection with the description of the diagrammatig view illustrated inFig. 6 and the mode of operation thereof which follows. is adriving-shaft connected to the armature. of the pilot-motor Laudprovided with a splinepin which is adapted to move in a spline-slot (seeFig. 2) in a hollow shaft 11, having a worm 3. To the lower end of theshaft 11 is secured a hollow collar 13, provided withinternally-arranged ball-bearings, adapted to sustain by a head a stemk, which supports, through an insulating-sleeve m, a metallic 01' otherconducting switching bar or disk 12, the free ends of which are adaptedto contact when said bar is drawn to its upper position by the pilotmotor at with yielding switching-contacts 14 15, the arrangement bemgsuch that by reason of the ball-bearings the switching. bar or disk 12will not be rotated with the shaft. The motor 4 and hollow shaft 11 aresupported in an iron frame 6, pivotally secured by means of a rod 9 to aframe 7, which is supported by the switchboard 8 and in which isjournaled the shaft 1 of the worm-wheel 2, the arrangement being suchthat through the rocking of the frame 6 around the rod 9 the worm 3 maybe moved into and out of mesh with the worm-wheel 2, as clearlyillustrated. The rocking of the frame 6 for causing said mesh iseffected through an electromagnet placed in suitable position. In thedrawing Fig. 2 said magnet is illustrated by two windings w w ofinsulated wire connected in the switching-circuit in a manner to behereinafter described, the function of said windings w 10' being tomagnetize the iron shaft 1, wormwheel 2, frames 6 and 7, and hencecomplete the magnetic-circuit between the worm-wheel 2 and the worm 3,so as to thereby bring said worm and worm-wheel into operative relationwith each other. 10 is a spiral spring located between an extension ofthe pivoted frame'fi and the frame 7, a nut and a bolt being providedfor limiting the outward throw of the pivotal parts, so that when thewindings w w are not energized the worm 3 will be just out of mesh withthe wormwheel 2.

Referring now to Figs. 4 and 5, I will describe the acceleration-controller, which is not generically different from the like apparatusdisclosed in my before-mentioned patent, in which patent, however, saidacceleration-controller was combined with brake mechanism, the novelty,in so far as this feature is concerned in the present application, lyingin improved detail construction and in the combination of such anacceleration-controller with the regulator in the manner to behereinafter described and as particularly pointed out in the claimswhich follow. This acceleration-controller is composed of a shaftinsulated from the lateral face thereof and electrically connected to acontact-ring carried on the'outer end of the hub of the fiywheel andmaking continuous contact with a brush connected to a binding-post, asshown. To the interior of the fiy-wheel is secured a spiral spring 38,wound around an extended interior hub and having its free end connecteddirectly to a disk or arm 33, provided with-a hub keyed to the shaft 52and carrying a second contact-ring, which is electrically connected to ayielding contact-point 22, adapted to make contact with thecontact-plate 22, 36 36 being bolts (see Fig.5) located in curved slots35 35 and so arranged thatthe initial relative position of the contacts22 22' may be adjusted. The contact-ring last referred to is connectedin turn by a brush to a second binding-post, as shown.

Referring now to the diagram for a full and clear understanding of thecircuits and circuit connections and the manner of connecting up andusing the entire apparatus, A and B represent, respectively, positiveand negative current-mains connected to a source of electrical energy.(Not shown.) M represents the armature of the motor to be controlled.and F the field thereof. C represents any well-known type of controller,here shown as a series of resistances provided with a controller-arm g,carried directly by the shaft 1,'driven' by the pilot-motor 4, (seeFigs. 1 and 2,) 17 being the armature, and 18 the field-coil, of saidmotor. (See Fig. 6.) f is the motor-circuit running from thecurrent-main A through the armature of the motor and the controllerapparatus to the negative main B, and .sis a shunt-circuit therefromincluding the field F of the motor. ff f ar e conductors which connectthe several parts of the apparatus together and to the current feedersor mains, as will be more fully described in connection with thedescription of the mode of operation. W is a weight carried at the freeend of thearm g, and It is a contact-plate located on one side of saidarm and adapted to make electrical contact with two stationary contacts51 32. v' is a pin located on the opposite side of the arm g and adaptedto operate a switch .v w in such manner as to open the circuit of thepilotmotor and to short-circuit its armature 17 when the arm 9 reaches.its upper limit and all of the resistance of the controller U is cut outof circuit between it and the curved contact-plate t. 21 28 arecontrolling-electromagnets adapted to operate upon armatures 20 and 27in a manner to be hereinafter speci- 29 and 30 represent parts of athermostatic cut-out device, 30 being a contact connected to one endofamagnet-winding '21 and 29 a bare metallic strip carrying the maincurrent of the motor M. Said strip 29 consists of two bands of metalsoldered together, having different coefiicients of expansion, such ascopper and zinc. When this strip is heated by the action of the current,it will assume a curved shape, the zinc being on the outside or convexside, and the contact 30 is so adjusted by set-screw 50 that it will betouched by strip 29 when said strip has reached a certain temperature.This bare metallic strip 29 may preferably be so incased that itsfacility for cooling may be approximately the same as that of thearmature conductors of the motor M. One mode of incasing said strip 29is illustrated in Fig. 6 at 51, which may-indicate a box surrounding thestrip, so as to protect it from the direct cooling action of the air.Thefacili'ty of the strip for cooling will. thus resemble that of theconductors on motor M, and being heated by the same current which heatssaid conductors its temperature will vary with their temperatu rethatis, the temperature of the strip will depend on the temperature of themotor which it is to protect. Hence it follows, for instance, that amoderate current acting on the motor and warming it up during aconsiderable time may heat the strip enough to cause it to close thecircuit at contacts 29 30 and, as hereinafter described, effect theopening of the motor-circuit, while, on the other hand,a much strongercurrent act ing for a short time may not cause that result, especiallyif the motor, and thus the strip. are fairly cool, as will be the caseupon starting the motor after a fairly long rest.

1 will now describe the operation of the entire apparatus, the circuitbeing shown as broken at theoperating-switch S'w. As illustrated in Fig.6, when the motor to be controlled isdisconnected from the circuit byopening the switch S'w all of the resistances of the controller C areconnected in series relation through the branch feederf, contactplate 5,and armature of the motor, and the switching-bar 12 is in its lowerposition. Upon closing the circuit at the switch Sw current flows fromthe positive-current main A by way of the branch feeder f through switchSw, contact 2 1, conductor f, circuit making and breaking contacts 26,coil 10 of the compound coil or w, through contactpoint 32,contact-plate it, contact-point 31, contactpoint 14, branch feeder f tothe negative main B. Consequently the worm 3 is drawn into mesh with 2.At the same time a branch circuit is closed from the switch SW7 throughthe contact-point 23, conductor f yielding contactpoint 22, andcontact-plate 22 of the acceleration-controller, Fig. 4, through thefieldcoil 18, current-interrupting contacts 19, and armature 17 of thepilot-motdr 4. Then by the worm-wheel wheel 2 acting as a nut andcausing this'upward movement to continue until the switching-bar 12 isbrought into firm electrical and mechanical contact with the yieldingcontacts 14 and 15 at the points of extreme upper movement. After thisoccurs rotary motion is still given to the worm 3, and now additionalwork is put upon the armature of the motor and the worm transmits to theworm-wheel rotary motion in the direction of the arrow, Fig. 1, thus'causing the conducting-plate carried at the outer end of the arm g toout out the successive coils of resistance in the controller orregulator, and hence to start and increase the speed of the armature Mof the motor to be controlled. VVhen'the arm g reaches its extreme upperlimit, the pin '5 is brought into mechanical contact with the free endof the switch is" w, shifting the same from connection with the contact16 into connection with the contact 16',thereby interrupting the circuitof the pilot-motor 4C and short-' circuiting the armature 17thereof,thusquickly stopping the same. It is to be noted, however, at this timethat the arm 7, carried bythe shaft 1, will not return to its ofiposition under the influence of the weight W after the pilot-motorhasbeen thus stopped, owing to the fact that when the switching-bar 12reached its upper limit and before the arm 9 was moved from its normalposition the circuit was closed through the other coil '10 of thecompound coil w w, switch-contact 15, switching-bar 12, switchcontact14, and branch feeder f, so that although the circuit was interruptedbetween the contact-plate 7a and contacts 31 32 when the arm 9 startedon its upward journey the worm 3 Will still be held in mesh with theworm-wheel 2 so long as the circuit be maintained closed through thisbranch w of the compound coil. Consequently the arm g will be held inits upper position, and the counterweight /V, acting through theworm-wheel 2 on the Worm 3, will press on the switching conducting-bar12 against the contacts 14: 15. This pressure prevents the shaft 1 ofthe regulator from rotating under the influence of the counterweightuntil the circuit through the winding w be interrupted either at theswitch 8 10 or at the contact 26 or by cessation of the voltage. Whencircuit f is opened either at 24 or at 26, the worm and worm-wheelwillbe put out of mesh by reason of the spring 10 and theobliquely-directed. cog-pressure, and

hence it follows that the shaft 11, with switching-bar 12, will drop,opening the motor-circuit at 14 and 15. The arm 7 of the regulator willalso drop by reason of the counterweight W and return to its oifposition, and the switch .v' 10 will be returned to contact 16, actuatedby its spring or weight. it will be noted that contact between 14 and 15cannot again be established before the arm g of the regulator hasactually reached its off position,

so that contact. is made between 31 and 32 in' the circuit of thewinding w. Hence the motor M can never be started before all itsstarting resistance is in circuit. The contact 26 is opened in case of aprolonged overload on the motor M in the following manner: The maincurrent of the motor M passing through the thermostatic device 29 willcause the same to close the branch circuit through the contact 30, coilu of magnet 28, and branch conductor f thereby interrupting the circuitrunning to the coil w. It will be noted that no sparking can ever occurat the contact between 29 and 30, since the making of said contact willcause 29 to lose its current. After the thermostatic device coolssuflieiently it will break contact at 30, and the motor M will thenagain start automatically, provided that the operating-switch S'wremains closed, and it will be readily understood that the preferredmanner of closing said switch Sw will depend upon the nature of theservice which the motor has to perform. To illustrate, this mode of op-,eration will be different if the motor is called upon to drive anelevator. from that of driving a pump feeding water into a tank. Whenthe circuit f is opened either at 16, 19, 22, or 23, the .circuit of thepilot-motor is broken, and said pilot-motor will stop more orlessquickly, and the movement of the regulator will be temporarily arrested.The contact 19 is broken in case the starting-current of the I motor Mexceeds a predetermined limit and in the following manner: Theelectromagnet 21 is energized by the main current, and when saidcurrent, reaches a certain strength the armature 20 carrying one of thecontacts 19 will be lifted. If so desired, this movement will alsoshort-circuit the armature 17 of the pilot-motor for the purpose ofstopping it quickly. The necessary adjustment of the magnet 21 fordifferent limits of starting-current is efiected by varying the lengthof the air-gap of the magnet 21, and this is done by clamping with thescrew 39 the vertical member 40 higher or lower in relation to themagnet-core. The contact 22 is opened by the acceleration-controller,(illustrated in Figs. 4 and 5,) and I will now describe the operation ofsaid apparatus upon the assumption that the same is mechanically.connected. or

geared to the shaft of the motor M through a belt or otherwise. It willbe apparent that should an abnormal currents'fiow be passed through themotor, so as to start it too suddenly when running without load or witha light load, the inertia of the fly-wheel 34 will cause it to lag, soas to effect an interruption of the circuit between the contact-plate 22and the yielding contact 22, thus stopping the pilot-motor andpreventing further movement of the regulator until the acceleration rateof the motor M is reduced so as to allow the contact-plate 22' to catchup with the contact 22, and thus reestablish the circuit of thepilot-motor, so that it may again move the regulator ,for obtainingfurther increase in speed of the motor M, such an arrangement making itpossible to thus automatically prevent any sudden starting of the motorM and to continuously effect such operation until the desired speed hasbeen attained.

The necessary adjustment of this apparatus for any desired limit ofacceleration is effected by varying the initial relative position ofcontacts 22 and 22', and this is done by shifting the contact-plate 22'on the fly-wheel in relation to the spring 38. I prefer this mode ofadjustment as being simpler than varying the strength of the spring, theinertia of the flywheel, or the angular breadth of the contacts,although my claims are intended to cover any manner of effecting thisadjustment.

Referring now to Fig.- 7, the shaft 11, rotated by thepreviously-mentioned shaft 5 of the pilot-motor 4, is connected with twolevers 41 and 41, of which one atatirne isadapted to be lifted, so thatby means of switching-bars 42 43 contact is made between a b and between0 d e for the running of the motor M in one direction, and likewise bymeans of switching-bars 42' 43 contact is made between a c and between 6d e for running in the opposite direction. The circuit connections forthis reversing-switch are clearly shown in diagram in Fig. 9. Whetherlever-41 orlever 41 will be lifted is determined by the position of therocking lever 44, which is adapted to swing to the right or left on apivot 45. This rocking of the lever is caused by one or the other of twomagnets 46 46, and the arrangement is such that one of the levers 41will be engaged by the rocking lever, which will furnish afulcrum 47 forthe proper lever while it is lifted, so as to establish the contacts forrunning in one direction. The other lever, 41', of which the fulcrum islocated on the stop 48', will only be lifted to the extent shown in Fig.f! and will make no contacts on its respective side. It will be notedfrom the diagram in Fig. 9 that the magnet-windings z z, operating therocking lever 44, are coupled. to contact 32, so that they receive nocurrent after the regulator-arm g has left its off position, and theyare therefore not apt to heat. A spring 49 (see Fig.- 7 keeps therocking lever in its position, either to the right or left. It will benoted in Figs. 6 and 9 that during the running of the motor M there isof the entire controlling apparatus 3 only one windingnamely, w-which isall the time energized. This winding w acts on a magnetic circuit whichhas no air-gap, so that the winding w requires only a few ampere-turns.For these reasons it is claimed that only a minimum of energy is wastedin the operation of the apparatus here described.

1 do not limit my invention to the details of structural apparatusillustrated in the accompanying drawings and hereinbefore described, asmany of the features may be materially departed from and still comewithin the scope of my claims hereinafter made.

1 believe it is broadly new with me to so devise and arrange acontrolling apparatus for an electric motor that the operatingswitch, bywhich the current is turned on and disconnected from the motor, may bemanipulated at will without conveying to the motor abnormal currents. Ibelieve it is broadly new with me to combine a circuit-interruptingacceleration-controller with an electric motor in such manner that on atoo sudden start of the motor the movement of its regulator will bestopped or prevented. I believe it is also broadly new with me toregulate the movement of a controller for an electric motor by apilot-motor so interconnected with switching mechanism that the entireoperation of control is automatically effected and that thp leastpossible attention is required on the part of the manipulation of theoperating-switch and that the least possible amount of energy is wastedin the operation of the switching mechanism.

Having thus described my invention, what I I claim, and desire to secureby Letters Patent of the United States, is

1. In apparatus for regulating electric motors the combinationof a motorand controller therefor with means for automatically operating thecontroller so as to obtain an increase in speed of the motor, and meansfor stopping said operating means when the rate of speed increaseexceeds a predetermined limit.

2. The combination of an electric motor, an automatic regulator forincreasing the speed thereof; and an accelerationcontroller for stoppingthe operation of said regulator when the rate of acceleration is greaterthan a predetermined amount.

3. An acceleration-controller consisting of a rotary disk or armconnected to and driven by the machine to be controlled;'a fly-wheeldriven through yielding means connected to said disk or arm; electriccontacts located on the arm and the fly-wheel, and means for adjustingthe initial relative position of said electric contacts.

, e. The combination of an electric motor; a regulator for increasingthe speed of said motor; a contact driven through rigid means by themotor, and a contact driven at the same average speed through yieldingmeans by the motor; in combination with means operated by the contactsfor stopping the regulator.

5. An electric motor provided with an automatic regulator adapted tosuccessively increase the speed of the motor; in combination with anacceleration-controller connected to and driven by the motor and adaptedto stop the regulator when the acceleration rate exceeds a predeterminedlimit.

6. The combination of an electric motor; an automatic regulator and anadjustable acceleration-controller all cooperating substan tially asdescribed.

7. The combination of an electric motor, a switch and a regulatortherefor; means for closing the switch and for moving the regulator;together with means for automatically stopping said movement when thestartingcurrent exceeds a predetermined amount.

8. The combination of an electric 'motor, a switch and a regulator forthe motor; a pilotmotor for closing the switch and for operating theregulator; together with means for stopping the pilot-motor when thestartingcurrent exceeds a predetermined limit.

9. The combination of an electric motor, a switch and a regulator forthe motor; a pilotmotor for operating said switch and regulator, and anelectromagnet having an armature operatively connected with contacts forbreaking. the circuit of said pilot-motor when the starting currentexceeds a predetermined amount.

10. The combination of an electric motor, a switch for said motor, amagnet-winding for holding said switch closed, a magnet for opening saidwinding, a thermostatic device actuated by an overload of current, saidmagnet becoming operatively energized upon the overheating of thethermostatic device.

11. The combination of an electric motor, a controlling-switch for saidmotor and means for releasing said switch, said means being operated bya magnet energized by current derived from the motor-circuit andconveyed through a metallic strip adapted to be heated so as to closethe derived circuit.

12. The combination of an electric motor, a regulator for said motor, apilot-motor for operating the regulator, and means for opening thecircuit of said pilot-motor when'the regulator has been moved to itslimit; together with means for moving or shifting the pilot- 'motor soas to disconnect it from the regulator. I

13. The combination of an electric motor with a switch; a regulator; ,apilot-motor for closing the switch, and means dependent on the load uponthe motor for intermittently operating the regulator through the agencyof the pilot-motor.

14. The combination of an electric motor, a main switch for said motor,a rotary pilotmotor for closing the switch, a magnet-winding forretaining the switch in closed position 1 and means'for opening saidmagnet-windin 15. The. combination of an electric motor;a regulator:apilot-motor mounted on a frame, and means for shifting the frame so asto connect or disconnect the pilot-motor from the regulator.

16. An electric motor provided with an operating-switch Sn, :1 mainswitch, a speedcontroller and a pilot-motor for controlling themovements of the-main switch and said speed-controller: together withmeans de-. pendent on the load upon the motor whereby the current canonly be passed through the motor in intermittent steps when theoperating-switch is closed.

1'7. The combination of an electricmotor; a speed -controller; a switchand a counterweight attached to the controller and adapted to hold theswitch in closed position.

18. The combination of an electric motor with switching contacts for themotor; a switching-bar and a controller, the controller being held fromrotating toward off position by the switching-bar as it presses againstthe switching contacts. 19. In a switching mechanism for electric motorsthe. combination of a controller moved through worm-gear by apilot-motor and switch contacts sustaining the end thrust of the worm.

20. The combination of an electric motor, a reversing-switch, means forclosing said switch, and a controller, the shaft of which is moved bythe same means after the reversingswitch is closed.

21. The eombina'tionof an electric motor; a regulator; electromagneticmeans dependent on the load upon the motor for intermittently operatingthe regulator, and aswitch adapted to be closed by thesame means beforethe regulator is moved.

22. The combination of an electric motor, a main switch for said motor,an operatingswitch having only one closed and one open position, andintermediate means for closing said main switch and for starting themotor with a predetermined limit of the startingcurrent.

23. The combination of an electric motor, an operating-switch havingonly one closed and one open position, and intermediate means forstarting the motor with a predetermined limit of acceleration.

24. The combination of an electric motor, an operating-switch havingonly one closed and onev open position, and intermediate means forstarting the motor with a predetermined limit of the starting-currentand with a predetermined limit of acceleration.

25,. In a reversing-switch for electric motors thc combination of apilot-motor operating two switching-levers and a rocking lever actuatedby one of two magnets so as to cause the lifting of one of theswitching-levers.

26. In a reversing-switch for electric motors, the combination of twoswitching-levers, means for lifting said levers, and means for causingone of the levers to close the circuit connections so as to start themotor.

27. In a reversing-switch for electric n10- tors. the combination of twoswitching-levers, one rocking lever,a'n operating-switch and twomagnets, one of which is energized through the operation of saidoperating-switch.

28. The combination of an electric motor: a circuit for the motor; ametallic strip included in the circuit; a branch circuit adapted to beclosed by the strip when heated, and means for opening themotor-circuit, said means being included in the branch circuit.

29. The combination of an electric motor; a switch; a metallic stripheated by the current of the motor; a branch circuit adapted to beclosed by the strip when heated; means for holding the switch closed,and means included in the branch circuit for opening the switch.

30. The combination of an electric motor; a circuit for the motor; aswitch; means for holding the switch closed; a magnet for opening theswitch; a contact for energizing the magnet by current derived from themotorcircuit, and a thermostatic device actuated by the motor-currentfor closing said contact.

31. The combination of an electric motor; a circuit and a switch for themotor; ametallic strip in the motor-circuit; a casing for the strip; abranch circuit including means for opening the switch, and a contact inthe branch circuit touched by the strip when it reaches a predeterminedtemperature.

32. The combination of an electric motor; a regulator; a pilot-motor:aworm-gear; means "for intermittently operating the regulator by thepilot-motor through the worm-gear, and means for disconnecting theworm-gear.

33. The combination of an electric motor; a regulator; a frame adaptedto be rocked around a fulcrum; means mounted on the frame for operatingthe regulator; means-for rocking the frame, and means for retarding theoper ation of the regulator. V

in testimony whereof I have sign'd my name to this specification in thepresence of two subscribing witnesses.

GUSTAF RENNERFELT.

Witnesses:

(J. J. KINTNER, M. F. KEATING.

